An Australian immigration inquiry has found that 18 criminals from Tonga have fraudulently obtained Australian visas.

Police in Tonga are under investigation after it was found that some officers had effectively wiped clean the criminal slate of 172 convicted Tongans, thereby enabling them to apply for work and residency visas overseas.

Australian immigration officials have found 18 such people holding permanent or temporary visas for Australia.

A Department spokeswoman says three of those visas have been cancelled.

The others are under further investigation and the department has not ruled out deportations.

New Zealand authorities have suspended Tongan visa applications after identifying about 40 visa-holders whose criminal convictions had been wiped.